CN109013676B - Method for promoting the transport of heavy metals from plant roots to aerial parts - Google Patents

Abstract

The invention discloses a method for promoting the transport of heavy metals from plant roots to aerial parts. In the method, multi-walled carbon nanotubes are used to promote the transport of heavy metals from plant roots to aerial parts. In the present invention, multi-walled carbon nanotubes are used to promote the transport of heavy metals in plants, increase the transport of heavy metals from plant roots to aerial parts, and simultaneously complete the effective removal of heavy metals in polluted environments. The method of using multi-walled carbon nanotubes to promote the transport of heavy metals from plant roots to aerial parts has the advantages of simple operation, easy implementation, wide applicability, low investment and operation cost, cleanliness and no pollution, no toxic effect on the environment, and the like. The method is an efficient, convenient and environmentally friendly method for promoting the transport of heavy metals in plants. At the same time, the method does not bring secondary pollution to the environment, is suitable for large-scale use, and has good application value and ecological benefits.

Description

Method for promoting the transport of heavy metals from plant roots to aerial parts

technical field

The invention belongs to the field of ecological restoration of heavy metal polluted environments, relates to a method for promoting the transport of heavy metals from plant roots to aerial parts, and particularly relates to a method for promoting the transport of heavy metals from plant roots to aerial parts by utilizing multi-walled carbon nanotubes.

Background technique

In recent years, with the rapid development of science and technology, the pace of industrialization, urbanization and agricultural intensification has been accelerating, and the environmental problems caused by heavy metal emissions have become increasingly serious. Heavy metals can directly enter the atmosphere, water and soil, and can also migrate in the above three media, thereby causing direct pollution to the environment. Since heavy metals can be bioaccumulated, they are particularly harmful to animals and plants, especially humans. At present, the commonly used treatment methods for heavy metal pollution include physical methods (extracting soil, soil replacement, deep ploughing, heat treatment, electrodynamic restoration), chemical methods (chemical leaching) and biological methods. Phytoremediation is a biotechnology that directly utilizes green plants to absorb, fix, filter and stabilize heavy metals. Heavy metals can enter plants from outside through non-metabolic absorption, metabolic absorption, symplast and apoplast transport, etc. Heavy metals are transported in the plant through transpiration and root pressure, and the plant can stabilize the freely moving heavy metals in the plant through cell wall binding, vacuolar compartmentalization, and chelation. Compared with other treatment technologies, phytoremediation belongs to in-situ restoration, which has the characteristics of low treatment cost and environmental friendliness, and has the effect of protecting topsoil, reducing erosion and soil erosion after vegetation is formed. Therefore, phytoremediation can be widely used in the reclamation of mines and the remediation of heavy metal contaminated sites.

Phytoremediation has been applied to the treatment of various heavy metal-contaminated sediments/soils, but in practical applications, it is found that when plants are used to treat heavy metal-contaminated sediments/soils, most of the heavy metals are only stabilized in the plant roots, and only a few Some heavy metals can be transported to the aerial parts of plants. However, heavy metals with stable roots may be re-released into the polluted environment when the sediment/soil environment changes, posing a threat to the environment and soil organisms again. It consumes a lot of manpower, material resources and financial resources, which leads to an increase in the follow-up processing cost. Therefore, how to efficiently and conveniently improve the transport of heavy metals in plants has become a major problem in the large-scale development of phytoremediation. At present, in the prior art, the bioavailability of heavy metals in the environment is mainly increased by adding chelating agents and combined microbial technology, but few technologies can promote the transport of heavy metals in plants. Therefore, it is necessary to find an efficient, convenient and environmentally friendly method to promote the transport of heavy metals in plants, which provides better support for the wide application of phytoremediation.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, and to provide a method for promoting the transport of heavy metals from plant roots to aerial parts, which is simple and easy to operate, easy to implement, low in investment and operation cost, clean and non-polluting, and non-toxic to the environment. .

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is:

A method for promoting the transport of heavy metals from plant roots to aerial parts uses multi-walled carbon nanotubes to promote the transport of heavy metals from plant roots to aerial parts.

The above method, further improved, includes the following steps: mixing the multi-walled carbon nanotubes with heavy metal contaminated sediment and/or heavy metal contaminated soil to obtain a heavy metal contaminated mixture; planting plants capable of enriching heavy metals in the heavy metal contaminated mixture to carry out Cultivation to complete the transport of heavy metals from plant roots to aerial parts.

The above method is further improved, and the concentration of the multi-walled carbon nanotubes in the heavy metal pollution mixture is 100 mg/kg-1000 mg/kg.

The above method is further improved, the purity of the multi-wall carbon nanotubes is 95%-100%; the inner diameter of the multi-wall carbon nanotubes is 5nm-10nm; the outer diameter of the multi-wall carbon nanotubes is 10nm ~20 nm; the length of the multi-walled carbon nanotubes is 10 μm to 30 μm; the density of the multi-walled carbon nanotubes is 1.9 g/cm ³ to 2.1 g/cm ³ .

The above method is further improved. The heavy metal in the heavy metal polluted sediment is at least one of cadmium, lead, zinc and copper; the heavy metal in the heavy metal polluted soil is at least one of cadmium, lead, zinc and copper. A sort of.

The above method is further improved. The initial concentration of cadmium in the heavy metal contaminated sediment is 15mg/kg～25mg/kg, the initial concentration of lead is 250mg/kg～350mg/kg, and the initial concentration of zinc is 200mg/kg～ 300mg/kg, the initial concentration of copper is 100mg/kg～200mg/kg; the pH of the heavy metal polluted sediment is 6～7; the cation exchange capacity of the heavy metal polluted sediment is 10cmol/kg～12cmol/kg.

The above method is further improved, the initial concentration of cadmium in the heavy metal polluted soil is 15mg/kg～25mg/kg, the initial concentration of lead is 250mg/kg～350mg/kg, and the initial concentration of zinc is 200mg/kg～300mg /kg, the initial concentration of copper is 100mg/kg～200mg/kg; the pH of the heavy metal polluted soil is 6～7; the cation exchange capacity of the heavy metal polluted soil is 10cmol/kg～12cmol/kg.

In a further improvement of the above method, the plant capable of enriching heavy metals is at least one of ramie, ryegrass, pokeweed, and boluola.

In a further improvement of the above method, the ramie is No. 3 Xiang ramie; the ramie is a 2-4 month old ramie seedling.

The above method is further improved, and the cultivation is performed outdoors; in the cultivation process, the temperature is controlled to be 20°C to 28°C, the humidity is 60% to 70%, and the illumination time is 10h/day to 14h/day.

The above method is further improved, and the cultivation time is 8 to 24 weeks.

Compared with the prior art, the advantages of the present invention are:

(1) the present invention provides a kind of method that promotes the transport of heavy metals from plant roots to aerial parts, utilizes multi-walled carbon nanotubes to promote the transport of heavy metals in plants, increases the transport of heavy metals from plant roots to aerial parts, and simultaneously completes the pollution Effective removal of heavy metals from the environment. In the present invention, multi-walled carbon nanotubes can be absorbed by plants and can be transported in plants, and heavy metals can be combined with multi-walled carbon nanotubes, so the use of multi-walled carbon nanotubes can effectively improve the migration rate of heavy metals, so that more The heavy metals are transported from the root system to the aerial part, and at the same time, it can also reduce the release of heavy metals in the root system and the possibility of heavy metal re-release, thereby reducing the possible secondary pollution of the environment and indigenous organisms caused by heavy metals in the root system. After being treated by the method of the present invention, only the aboveground parts of plants can be harvested to remove the heavy metals from the polluted sediment/soil. Compared with the traditional phytoremediation technology, the method of the present invention eliminates the need to extract the root system from the environment. , treatment of heavy metals in the root system and other steps, which greatly simplifies the treatment steps and reduces the treatment cost. The method of the invention has the advantages of simple operation, easy implementation, wide applicability, low investment and operation cost, cleanliness and no pollution, no toxic effect on the environment, etc., and is an efficient, convenient and environmentally friendly method that can promote the transport of heavy metals in plants At the same time, the method will not bring secondary pollution to the environment, is suitable for large-scale use, and has good application value and ecological benefits.

(2) In the method of the present invention, multi-walled carbon nanotubes are used to promote the transport of heavy metals in plants, wherein multi-walled carbon nanotubes are an environment-friendly carbon material that will not pollute groundwater resources and thus will not cause environmental damage. Secondary pollution, and the multi-walled carbon nanotubes used in the present invention can be used as a sediment/soil conditioner to improve the environment of the sediment/soil, such as adjusting pH, increasing soil fertility and the like.

(3) In the method of the present invention, the preferred ramie is an important fiber crop, known as "Chinese grass", widely distributed in my country, high in yield, and has the advantages of wide sources and low cost. Ramie is a perennial plant with strong regeneration ability and developed root system. After being treated by the method of the present invention, only the aerial part of the plant needs to be harvested, so the developed root system of the underground part can maintain water and soil, control water and soil loss, and reduce soil erosion; On the other hand, the ramie used can be planted and benefited for many years; and in the aboveground part of the ramie harvested, the longer ramie fibers can be used for industrial textiles, such as making fishing nets, blankets, sacks, etc., while the shorter ramie fibers can be used for industrial textiles. As high-grade paper, gunpowder, rayon and other raw materials, it has good use value and application prospects.

Description of drawings

To make the purposes, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention.

Fig. 1 is a graph showing the influence of different concentrations of multi-walled carbon nanotubes on the transport effect of heavy metals in ramie in Example 1 of the present invention.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

In the following examples of the present invention, unless otherwise specified, the materials and instruments used are commercially available, the techniques used are conventional techniques, and the equipment used is conventional equipment, and the obtained data are the average values of three or more repeated experiments.

Example 1

A method for promoting the transport of heavy metals from plant roots to aerial parts, using multi-walled carbon nanotubes to promote the transport of heavy metals from plant roots to aerial parts, comprising the following steps:

(1) Take heavy metal contaminated sediment from the Changsha section of the Xiangjiang River, air-dry it under natural conditions, and sieve it for later use. The main heavy metal pollutant in the air-dried heavy metal contaminated sediment is cadmium, and the initial concentration of cadmium is 22.44 mg/kg. The pH of the air-dried heavy metal contaminated sediment was 6.76, and the cation exchange capacity was 11.65 cmol kg ^-1 .

(2) adding multi-walled carbon nanotubes of different weights to the heavy metal-contaminated sediment after air-drying in step (1) in a solid-solid mixing manner to obtain heavy metal-contaminated mixtures with different concentrations of multi-walled carbon nanotubes, wherein the heavy metal pollution The concentrations of multi-walled carbon nanotubes in the mixture were 0, 100 mg/kg, 500 mg/kg, 1000 mg/kg. The purity of the multi-walled carbon nanotubes used was 98%, the inner diameter was 8 nm, the outer diameter was 15 nm, the length was 20 μm, and the density was 2.0 g/cm ³ .

(3) 2-month-old ramie seedlings (Xianglimie No. 3) were respectively transplanted into the heavy metal contaminated mixtures with different multi-walled carbon nanotube concentrations obtained in step (2) (that is, the heavy metal contaminated sediment containing multi-walled carbon nanotubes). ), and the cultivation conditions are as follows: the light time is 10h-14h, the temperature is 20°C-28°C, and the humidity is 60%-70%. The ramie numbers are A0, A100, A500, and A1000, which correspond to the ramie cultivated in the heavy metal pollution mixture with the multi-walled carbon nanotube concentrations of 0, 100 mg/kg, 500 mg/kg, and 1000 mg/kg, respectively.

After 3 months of cultivation, the ramie A0, A100, A500, and A1000 were harvested, and the heavy metal cadmium content in the ramie was measured by graphite-atomic absorption spectrometry, and the cadmium content (accumulation) of the aerial parts of each plant and the whole plant was calculated. , the results are shown in Table 1 and Table 2.

Table 1 The accumulation of cadmium in the aerial parts of ramie after treatment with different concentrations of multi-walled carbon nanotubes

Table 2 The accumulation of cadmium in the whole ramie after treatment with different concentrations of multi-walled carbon nanotubes

As can be seen from Table 1, compared with the control group without adding multi-walled carbon nanotubes, the present invention significantly increases the accumulation of cadmium on the ground of ramie after using multi-walled carbon nanotubes for treatment, wherein the concentration of multi-walled carbon nanotubes is 100mg. When ramie/kg, 500mg/kg, and 1000mg/kg, the corresponding accumulation of cadmium in the aerial part of ramie was 24.12 μg/strain, 32.94 μg/strain, and 29.48 μg/strain, respectively, which was comparable to the control group without multi-wall carbon nanotubes. The accumulation of cadmium increased by 26.88%, 73.28% and 55.08%, respectively. It can be seen from Table 2 that when the concentration of multi-walled carbon nanotubes is 500 mg/kg and 1000 mg/kg, the accumulation of cadmium in the whole ramie is only increased by 17.96% and 5.78%, respectively, which is far lower than the same concentration of carbon nanotubes. The accumulation of cadmium in the aerial part of ramie after treatment increased, and when the concentration of multi-walled carbon nanotubes was 100 mg/kg, the accumulation of cadmium in the whole ramie even decreased by 5.18% compared with the control. It can be seen from Table 1 and Table 2 that the multi-walled carbon nanotubes added in the present invention can promote the accumulation of heavy metals in the aerial part.

According to the accumulation level of heavy metals in ramie, the ratio of cadmium accumulation in aerial parts to cadmium accumulation in roots was obtained. The results are shown in Table 3.

Table 3 The ratio of cadmium accumulation in the shoot and root of ramie treated with different concentrations of multi-walled carbon nanotubes

As can be seen from Table 3, compared with the control group without adding multi-walled carbon nanotubes, the ratio of cadmium accumulation in the aerial part of ramie to the root system of ramie after treatment with multi-walled carbon nanotubes is significantly increased, wherein the concentration of multi-walled carbon nanotubes is At 100 mg/kg, 500 mg/kg, and 1000 mg/kg, the ratios of the cadmium accumulation in the shoots and roots of the corresponding ramie were 0.61, 0.69, and 0.68, respectively, which were 1.61 times, 1.82 times, and 1.79 times that of the control group. The multi-walled carbon nanotubes added in the present invention can promote the transport of heavy metals from the underground part to the above-ground part.

According to the calculation of the concentration of heavy metals in ramie, the transport coefficient of heavy metal cadmium in ramie was obtained, that is, the ratio of the concentration of cadmium in the aerial part to the concentration of cadmium in the root system. The results are shown in Figure 1. Fig. 1 is a graph showing the influence of different concentrations of multi-walled carbon nanotubes on the transport effect of heavy metals in ramie in Example 1 of the present invention. As can be seen from Figure 1, compared with the control group without adding multi-wall carbon nanotubes, the present invention adopts the multi-wall carbon nanotubes to process the heavy metal cadmium in the ramie The transport coefficient of cadmium is significantly increased, and wherein the concentration of multi-wall carbon nanotubes is 100mg/kg. The transport coefficient of heavy metal cadmium in ramie can reach 0.65, while the transport coefficient of cadmium in the control group is only 0.36, which shows that the present invention can well promote the transport of heavy metals in plants by adding multi-walled carbon nanotubes. Transport more heavy metals in the root system to the aerial parts.

Comparative Example 1

A method of utilizing nanometer zero-valent iron (commercially available or obtained by conventional methods) to promote the transport of heavy metals from plant roots to aerial parts is basically the same as that of Example 1, the difference is only that: in the step (2) of Comparative Example 1, nanometer Zero-valent iron replaces multi-walled carbon nanotubes. Ramie numbers are B0, B100, B500, and B1000, which correspond to ramie cultivated in heavy metal contaminated mixtures with nano-zero-valent iron concentrations of 0, 100 mg/kg, 500 mg/kg, and 1000 mg/kg, respectively.

According to the calculation of the heavy metal cadmium content in the ramie after the nano-zero valent iron treatment, the ratio of the cadmium accumulation in the aerial part of the ramie after the nano-zero valent iron treatment to the cadmium accumulation in the root system was obtained. The results are shown in Table 4.

Table 4 The ratio of cadmium accumulation in the shoot and root of ramie treated with different concentrations of nano-zero valent iron

It can be seen from Table 4 that compared with no nano-zero-valent iron added, the addition of nano-zero-valent iron with a concentration of 100 mg/kg and 500 mg/kg can increase the ratio of cadmium accumulation in the aerial part of ramie to the root system, but the increase is only 11%. and 8%, which is far less than the increase after adding multi-walled carbon nanotubes in Example 1 of the present invention. In particular, after adding nano-zero valent iron with a concentration of 1000 mg/kg, the ratio shows a negative increase, which shows that the present invention adopts The multi-walled carbon nanotubes can more efficiently promote the transport of heavy metals from plant roots to aerial parts.

The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All the technical solutions under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, improvements and modifications without departing from the principles of the present invention should also be regarded as the protection scope of the present invention.

Claims (4)

1. a kind of method that promotes heavy metal to be transported to aerial part from plant root system, it is characterized in that, utilize multi-wall carbon nanotube to promote the transport of heavy metal from plant root system to aerial part, comprise the following steps: by multi-wall carbon nanotube and heavy metal pollution The sediment is mixed to obtain a heavy metal pollution mixture; the plants capable of enriching heavy metals are planted in the heavy metal pollution mixture for cultivation to complete the transport of the heavy metals from the plant roots to the aerial parts; the concentration of the multi-walled carbon nanotubes in the heavy metal pollution mixture is 500 mg/kg; the heavy metal in the heavy metal-contaminated sediment is at least one of cadmium, lead, zinc, and copper; the initial concentration of cadmium in the heavy-metal-polluted sediment is 15 mg/kg to 25 mg/kg; The initial concentration is 250mg/kg～350mg/kg, the initial concentration of zinc is 200mg/kg～300mg/kg, the initial concentration of copper is 100mg/kg～200mg/kg; the pH of the heavy metal contaminated sediment is 6～7; The cation exchange capacity of the heavy metal-contaminated sediment is 10cmol/kg～12cmol/kg; the plant capable of enriching heavy metals is ramie; the purity of the multi-walled carbon nanotubes is 95%～100%; The inner diameter of the carbon nanotube is 5nm-10nm; the outer diameter of the multi-wall carbon nanotube is 10nm-20nm; the length of the multi-wall carbon nanotube is 10μm-30μm; the density of the multi-wall carbon nanotube is 1.9 g/cm ³ to 2.1 g/cm ³ . 2. method according to claim 1, is characterized in that, described ramie is Xiang ramie No. 3; Described ramie is ramie seedling of 2～4 months. 3. method according to claim 1, is characterized in that, described cultivation is carried out outdoors; In described cultivation process, control temperature is 20 ℃～28 ℃, humidity is 60%～70%, and illumination time is 10h/day ~14h/day. The method according to claim 1, wherein the cultivation time is 8 to 24 weeks.

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